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Neoplasia > carcinogenesis > Flashcards

carcinogenesis Flashcards

1
Q

What is carcinogenesis?

A

The transformation of normal cells to neoplastic cells through permanent genetic alterations of mutations

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2
Q

what is the difference between carcinogenesis and oncogenesis?

A

carcinogenesis only applies to malignant neoplasms, but oncogenesis applies to benign and malignant neoplasms

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3
Q

What is a carcinogen?

A

agents known or suspected to cause tumours

they act on DNA, i.e. they are mutagenic

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4
Q

What percentage of cancer risk is environmental and what percentage is genetic?

A

85% environmental

15% genetic

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5
Q

Why is it difficult to identify the carcinogen that caused a cancer?

A
  1. latent interval may be decades
  2. complexity of environment (we are exposed to so many carcinogens)
  3. ethical constraints (of directly testing carcinogens on humans)
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6
Q

Give examples of cancer that was discovered using epidemiological evidence

A
  1. hepatocellular carcinoma - uncommon in the USA/UK, but common in areas with high Hep B/C and mycotoxins
  2. oesophageal carcinoma - high incidence in Japan, China, Turkey and Iran. Gullet cancer in chickens was also observed in the high-incidence area, suggesting the presence of cancer-causing substances in the environment.
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7
Q

Give examples of occupational/ behavioural cancer causes

A
  1. lung cancer and smoking
  2. bladder cancer and dye and rubber industries, beta-naphthylamine (aromatic amines)
  3. scrotal cancer and chimney sweeps due to polycyclic aromatic hydrocarbons
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8
Q

Give examples of direct evidence of cancer causation

A
  1. Thorotrast - used as a contrast medium, is a clolloidal suspension of thorium and is irreversibly ingested by phagocytes, causes angiosarcoma
  2. chernobyl nuclear reactor explosion - release of radioactive iodine caused increase in thyroid cancer in Ukrainian children
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9
Q

Give examples of experimental evidence of cancer causation

A
  1. incidence of tumours in lab animals
  2. cell/tissue cultures
  3. mutagenecity testing in bacterial cultures
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10
Q

Give disadvantages of experimental evidence

A
  1. animals/ cultures may metabolise agents differently to humans
  2. bacterial mutation may not mean carcinogenicity in humans
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11
Q

State the classes of carcinogens

A
  1. chemical
  2. viral
  3. ionising and non-ionising radiation
  4. hormones
  5. parasites
  6. mycotoxins
  7. miscellaneous
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12
Q

What is the name given to the inactive form of a chemical carcinogen and what is this converted to?

A

pro-carcinogen converted to ultimate carcinogen

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13
Q

what chemical can cause lung cancer and what is this due to?

A

Polycyclic aromatic hydrocarbons due to smoking

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14
Q

What chemical can cause skin cancer and what is this due to?

A

Polycyclic aromatic hydrocarbons due to mineral oils

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15
Q

What chemical causes bladder cancer and what is this due to?

A

beta-naphthylamine, which is an aromatic amine; due to rubber and dye

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16
Q

What compound causes gut cancer?

A

nitrosamines

17
Q

What compound causes leukaemia?

A

alkylating agents

18
Q

List some chemical compound groups that can cause cancer

A
  1. polycyclic aromatic hydrocarbons
  2. aromatic amines
  3. nitrosamines
  4. alkylating agents
19
Q

Give examples of cancer caused by radiation

A
  1. skin cancer in radiographers
  2. lung cancer in uranium miners
  3. thyroid cancer in Ukranian children
  4. UV light (A or B) causes basal cell carcinoma, melanoma and squamous cell carcinoma and there is increased risk with xeroderma pigmentosum
20
Q

Give examples of biological causes of cancer

A

hormones, parasites, mycotoxins

21
Q

Give examples of cancer caused by hormones

A

high oestrogen, increases breast cancer and endometrial cancer

22
Q

Give an example of cancer caused by mycotoxins

A

hepatocellular carcinoma caused by aflatoxin B1

23
Q

Give examples of cancer caused by parasites

A
  1. Chlonorchis sinensis = cholangiocarcinoma, mutated epithelial cells of bile ducts
  2. shistosoma = bladder cancer
24
Q

Give examples of miscellaneous carcinogens

A
  1. asbestos

2. metals (arsenic, chromium, and nickel)

25
Q

Give examples of host factors that contribute cancer

A 
race
consitutional factors e.g. age, gender, inherited predisposition 
diet
premalignant lesions
transplacental exposure
26
Q

Give an example of where race plays a role in cancer development

A

skin cancer in blacks is reduced as they have more melanin

27
Q

Give maples of inherited predispositions that cause cancer

A
  1. familial polyposis coli

2. retinoblastoma

28
Q

Give examples of pre-malignant conditions that can develop into cancer

A

colonic polyps
cervical dysplasia (CIN)
ulcerative colitis
undescended testis

29
Q

Give an example of transplacental carcinogenesis

A

Diethylstiboestrol - DES was shown to cause clear cell carcinoma, a rare vaginal tumor, in girls and women who had been exposed to this drug in utero

30
Q

List ways in which we can identify the cause of cancer

A

epidemiological evidence
occupational/ behavioural
direct evidence
experimental

31
Q

Give examples of oncogenic viruses

A
  1. Epstein-Barr virus = Burkitt’s lymphoma (B cell lymphoma)
  2. HPV - cervical cancer, common wart
  3. Hep B and C - hepatocellular carcinoma
  4. HHV-8 = Kaposi’s sarcoma
32
Q

Give reasons why increasing age increases risk of cancer

A
  1. long latent period
  2. cumulative risk of exposure to carcinogens
  3. accumulations of mutations
  4. protective effect of natural killer cells lost with age
33
Q

Give examples of genetic changes that are required to change a cell into a neoplastic cell

A
  1. loss/inactivation of both copies of a tumour suppressor gene (e.g. p53)
  2. activation/ abnormal expression of oncogenes
  3. telomerase expression
34
Q

Give two roles of a tumour suppressor gene

A
  1. repair DNA damage

2. inhibits proliferation promotes death of cells (apoptosis) with damaged DNA

35
Q

Give examples of products of oncogenes

A

growth factor
receptor for a growth factor
intracellular signalling protein
transcription factor

Neoplasia (5 decks)

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